The invention relates generally to a knitting machine for producing a knitted product.
A known machine of this type configured as a circular knitting machine (PCT WO 2004/079 068 A2) is distinguished in that directly after its exit from a drafting assembly the fibre material used for knitting is transformed into a yarn by means of a spinning device. It is particularly advantageous that it is transformed into a temporary yarn with genuine twists and the temporary twists of the fibre material are retained during the entire transport process. As a result, it is possible, on the one hand, to transport the fibre material over longer distances from the drafting assembly to an associated knitting system in spite of its low strength compared to usual yarns, since as a result of this artificial handle the fibre material formed into a temporary yarn meets all the strength requirements on the transport path from the drafting assembly to the knitting system. Therefore, the fibre material can be transported over long distances without there being any risk of it unraveling or tearing. On the other hand, on the short distance from the outlet end of the spinning device to the knitting system, i.e. until the fibre material runs into the knitting needles, the twists in the temporary yarn are reduced to zero (false twist principle), so that the fibre material actually processed in the knitted product does not consist of a twisted yarn, but of substantially untwisted staple fibres arranged parallel to one another. Consequently, a knitted product of extreme softness is obtained as end product.
Alternatively, the spinning device can be configured to form a permanently bonded, in particular a so-called unconventional yarn and can be configured e.g. as an air spinning device (cf. e.g. EP 1 518 949 A2 and EP 1 826 299 A2). Such a yarn also has some twists or windings, but is not a yarn in the classic sense such as e.g. a bundle or covering yarn. The spinning process is preferably adjusted so that, as in the case of the temporary yarn described above, a sufficiently firm sliver is formed that is sufficient for the desired transport purposes, but a sufficiently soft knitting product is still obtained.
A perceived disadvantage is that the known machine is provided with a suction element on the side of the thread guide remote from the spinning device and on the rear side of the needles. The purpose of this suction element should be to tension the fibre material coming from the thread guide radially to the needle cylinder axis and keep it tensioned, so that it is taken up by the knitting needles raised into a fibre pick-up position and processed into stitches. Moreover, the suction element has been considered necessary hitherto to facilitate start-up of the circular knitting machine, in particular after a short machine stop or a break in the fibre material.
Besides the additional costs, such a suction element above all involves a high energy consumption, since such a suction element must be provided at each of the 48 or more knitting systems, for example, of the circular knitting machine. In addition, there is the risk of the suction element not taking up all the entrained fibres in the extracted fibre material and therefore of undesirable accumulations of fibres (so-called lumps) forming that drop into the tubular knit and foul it.
Working from this, the technical problem forming the basis of the invention is to configure the machine of the above-indicated type without increasing the structural expenditure so that the suction element can be omitted altogether.
The invention is based on the concept of using blast air used for the temporary yarn in the transport tube at the same time to insert the fibre material into the knitting needles and/or to transport the fibre material to behind the needle line formed by the knitting needles. This is achieved with the features of the invention without the blast pressure in the transport tube having to assume undesirably high values and without the risk of the fibre material and detached fibres accumulating in an interstice between the transport tube and the thread guide or in the passage of the thread guide, of undesirable turbulences occurring and/or other faults occurring that prevent the insertion of the fibre material into the knitting needles or impair the finished knitted product. Apart from this, there result the additional advantages that the blast air flow discharging from the passage of the thread guide causes a constant self-cleaning of the knitting needles and can also be used advantageously during the start-up of the circular knitting machine.